Z6 House

Photo credit: Amy Sims

Site Description

The project is a single-family residence that was added to a multifamily-zoned lot with an existing duplex. Prior to construction, this portion of the site was covered in hardscape and lawn. To recreate the open feeling of the space prior to construction, the project team incorporated a green roof into the project. Plantings on the roof are native species, mostly sedums, native grasses, and rushes. The site also includes a small vegetable and herb garden. The landscaping around the house consists of newly planted native groundcover, shrubs, and trees.

Because the neighborhood was originally sited on sand dunes that were paved over for development, creating hills, the project site is sloped. Site drainage, stormwater use, and stormwater infiltration on site are important issues in this ecology. Rainwater collected from the roof, combined with stormwater diverted from site drains and swales, is stored in a cistern and used to irrigate the gardens.

• Lot size: 6,233 ft2
• Previously developed land

Water Conservation and Use

The 3,500-gallon water cistern sits below grade; collected water is pumped up to irrigate the roof garden. The irrigation system on the roof consists of boxes lined with an EPDM membrane and filled with evaporative-control-system chambers that help keep moisture in the planting medium, which is a mixture of sand and perlite. The bottom three inches of each box is kept moist; water is pumped up to the roof as needed to maintain this level. Excess water flows out of the boxes and back to the cistern.

The ground-level landscaping is watered with graywater from the showers, tubs, bathroom sinks, and clothes washer, via a subterranean irrigation system. All irrigation is controlled by a device that monitors humidity in the atmosphere and prevents irrigation when it is raining.

Low-flow plumbing fixtures throughout the house further reduce the home's use of potable water.

Water Data

• Indoor potable water use: 17,000 gal/yr (64,400 liters/yr)
• Outdoor potable water use: 12,000 gal/yr (45,400 liters/yr)
• Total potable water use: 29,000 gal/yr (110,000 liters/yr)
• Potable water use per occupant: 29,000 gal/person/yr (110,000 liters/person/yr)
• Potable water use per unit area: 11.7 gal/sq ft (476 liters/sq meter)

Green Strategies

• Landscape Plantings
  • Landscape with indigenous vegetation
  • Landscape with edible plants
• Demand for Irrigation
  • Select plants for drought tolerance
• Irrigation Systems
  • Recycle graywater for landscape irrigation
  • Use automatic controls to improve efficiency and effectiveness of irrigation system
  • Use a moisture meter to control outdoor irrigation
• Site Planning
  • Provide for solar access

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Our thanks to the ENERGY STAR program of the U.S. Environmental Protection Agency, and to the U.S. Department of Energy, and to BuildingGreen, Inc. for hosting the submission and judging forms.

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